Principal investigators: Larry Hammell & Gerald Johnson
Co-Investigators: Diana Jaramillo, Raju Gautam, & Annette Boerlage
The major challenges facing the halibut aquaculture industry are the slow growth rate of halibut (36 months to market size) and large, within-group variability in growth of farm-raised fish. Common husbandry practices specific to halibut farming have not been studied, particularly for the juvenile stage (5g to 200g). This study evaluated the effects of stocking density, tank shelving, and water temperature on growth of juvenile halibut. Retrospective data was also analyzed in an effort to quantify the variation of the survival and growth of farmed halibut from hatchery to grow-out.
We evaluated the effects of shelving, as a means of increasing resting surface area, on growth of Atlantic halibut, with two groups of fish at different densities. Halibut use primarily only the bottom surface of tanks, unlike salmon, which are found throughout the water column, so density was measured as percent coverage of the tank bottom. We found that the fish made active use of the shelves provided, which was taken as an indication of enhanced conditions. However, by the end of the experiment, fish in the lower density group had a significantly higher weight gain than those in the higher density treatment, but the inclusion of shelves was found to have no effect on weight gain.
We are also analyzing retrospective data to try to identify specific factors that might influence survival and grow rate, including water temperature, and feed management. Preliminary findings indicate fluctuations in mortality are seasonal and might be related to timing of regrouping or weight variation in a tank. Further analyses are being conducted.